At the entrance area of one of the institute buildings of the
university of Granada in the calle Profesor Adolfo
Rancaño a sculpture of the Möbius strip can be found. A plaque
commemorates to the German mathematician and astronomer
August
Ferdinand Möbius and also explains the particularities of this non-orientable
surface. But it irritates that his year of death given there differs about 8 years from
other sources.

He stood out with his studies concerning celestial mechanics and
renewed the projective geometry as well as the algebraic topology. In mathematics he gained
fame due to his work a peculiar band, nowadays called Möbius strip. It is a matter of
a non-orientable surface with only one side and a boundary consisting of one
curve.

If we assume that a surface possesses two faces. To colour it
completely it is necessary to lift up the pencil in order to move from one face to the
other. But we may draw a line on the Möbius strip which runs alongside through the
whole band returning to the starting point without lifting up the pencil. By a similar
experiment where we put a finger-tip on the boundary of the strip. We may completely move it
along the boundary also without lifting it. This shows that the boundary of the band
consists of exactly one line.

This figure possesses much more interresting geometrical and
topological properties. Let us make a Möbius strip from a piece of paper and cut it up
in its mid such that the longitudinal section runs parallel to the boundary. Surprisingly
this section does not yield two pieces but a band with two faces and a boundary consisting of two curves.

Möbius was a pedantically and orderly scientist, a trait his was
also showing in his everyday life. It was told of him that every day he said when leaving
his house: "3S und Gut", in order to forget not "Schlüssel" (key), "Schirm" (umbrella),
"Sacktuch" (handkerchief), "Geld" (money), "Uhr" (watch) und "Taschenbuch"
(pocket-book).

The translation of the Spanish text to German has been performed by my
colleague Christoph Mark.